Note: Descriptions are shown in the official language in which they were submitted.
CA 02344724 2004-11-12
VENTILATED PLASTIC BAG
Field Of The lnvention
This invention relates to a ventilated plastic bag particularly adapted for
carrying hot food from fast food restaurants, a pack of such bags, and a
dispensing
system utilizing such bags.
Background Of The Invention
Since the 1970's, plastic bags have been replacing paper bags in the United
States for the grocery and retail products industries because of the superior
strength
and inherent moisture resistant properties and strength of plastic, among
other
things.
10 These plastic bags have taken various shapes and forms including T-shirt
type plastic bags which include front and rear wall sections integrally
connected
together by gussetted side walls and connected at the bottom to define a
closed
bottom on the bag. At least a part of the top of the front and rear wall
sections are
open at the tops to define an open mouth and laterally spaced handles which
are
15 integral with the wall sections extend upwardly from opposed sides of the
mouth
portions for carrying of the bags. This type of plastic bag is illustrated
assignee's
prior U.S. Patent 4,676,373.
Other types of plastic bags include what is known in the industry as a die-
20 cut handle bag which has front and rear wall sections preferably connected
by
Qussetted side wall sections integrally extending therefrom and positioned
therebetween and wherein the bottom of the bag is closed and the top of the
bag is
open. These die-cut handle bags include a cut out hole, preferably of a kidney-
shape, positioned generally cemrally of a top area of the bag for receiving
fingers
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CA 02344724 2004-11-12
of the user for carrying of the bag. Other bag constructions have been
proposed
with handle means provided in top areas of the bag formed by a cut out of
front
and rear wall sections.
All of these bags are usually utilized in a pack of a plurality of bags and in
a dispensing system in which the bag pack is mounted in generally vertically
suspended position for successive removal of the bags by a user.
Notwithstanding the success of plastic bags and replacement of plastic bags
in the grocery and retail products industries, paper bags have for the most
part
continued to be used in the fast food restaurant industry for packaging and
carrying
hot foods. There are a number of problems associated with the use of such
paper
bags in the fast food restaurant industry, including the difficulty in
handling of the
paper bags, the inherent opaque nature of the paper bags resulting in the
inability to
see the hot food items packaged in the bag and resulting mistakes in filling
customers' orders, the inherent weaknesses in the bags when they become moist
or
the like, etc. On the other hand, plastic bags have not been used for
packaging and
transporting hot foods in the fast food restaurant industry primarily because
of the
problem which occurs with moisture collecting on the insides of the plastic
bag
when filled with hot foods. This moisture will condensate and cause the food
to
get soggy and will wet the hand of the user when reaching into the bag.
In an attempt to overcome this problem with the use of plastic bags in the
fast food restaurant industry, a T-shirt type plastic bag for carrying hot
foods was
developed, as illustrated and described in assignee's prior U.S. Patent
5,362,152.
The T-shirt type plastic bag of this prior patent provided apertures extending
through
at least one of the wall sections of the bag for providing a path for venting
air flow
from the outside of the bag and through the inside of the bag when the bag is
carrying
hot food. The apertures comprise a generally semi-circular shaped cut out
defining a
flap portion which opens up to produce a generally half moon-shaped aperture.
These C-shaped apertures were preferably spaced about 2-1/2" to 3" apart and
were of relatively large sizes to allow the above-described flow of air.
While this ventilated plastic bag construction of assignee's prior U.S.
patent overcame some of the previous problems presented with paper bags and
provided a plastic bag construction which could be utilized by the fast food
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CA 02344724 2001-09-19
restaurant industry, it did not sufficiently prevent condensation within the
bag.
Because of the size of the C-shaped vent apertures, a spacing of 2" to 3"
apart was
necessary to preserve the strength of the bag. However, this created dead
zones
within the bag with no airflow and thus did not sufficiently prevent
condensatkn from
forming on the inside of the bag.
Obiect and Summary of the Invention
Accordingly, it is the object of an aspect of this invention to provide a
ventilated plastic bag which is particularly adapted for carrying hot foods
from fast
food restaurants and which will overcome the problems discussed above.
By this invention it has been found that the above object may be accomplished
by providing a ventilated plastic bag comprising any desired construction
including at
least front and rear wall sections connected together to define a closed
bottom area
and an open top area and handle means in the top area which is at least
partially
formed by a cut out ofd the front and rear wall sections resulting in reduced
strength
regions with resulting high potential for tearing in the front and rear wall
sections
around at least a part of the cut out. Closely spaced micro-perforations
extend
through the wall sections in at least a major portion of the plastic bag to
provide
desired ventilation to an interior food carrying area of the plastic bag.
Micro-perforations have been utilized in plastic bags for purposes other than
in the fast food industry, i.e. plastic bags with micro-perforations have been
utilized
for holding loafs of bread and have been utilized with zip-lock bags for
containing
vegetables or the like food products. In these bags, the pattern of micro-
perforations
consumed substantially the entire surface areas of the bags.
Micro-perforations in a plastic bag to be utilized in the fast food industry
would have two primary, yet sometimes conflicting purposes. These are to
prevent
condensation within the bag and to keep the food in the bag warm. Closely
spaced
micro-perforations provide virtually 100% venting coverage in the food
carrying
portion of the bag while keeping the food warm in the bag. By placing small
perforations close together, all surface areas of the bag having the
perforations are
subjected to a small airflow from the natural convection created to prevent
condensation from forming on the inside surface of the bag. The micro-
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perforations, as opposed to large vent openings, keep the food warmer while
providing desired ventilation.
However, it has been determined by this invention that these closely spaced
micro-perforations tend to weaken the resistance to tear in the bag and if
placed
along substantially the entire surface area (as had been done in prior micro-
perforated plastic bread and vegetable bags) and in the reduced strength
regions
created by the cut out utilized to form the handle means in the bag, and
create
greater tear propagation providing problems in use of the bags. Therefore, in
accordance with this invention the closely spaced micro-perforations are
positioned
in a major portion of the plastic bag other than the reduced strength regions
to
provide the desired ventilation to an interior food carrying area of the bag
while
not further weakening the reduced strength regions of the bag and increasing
the
potential for tearing.
The ventilated plastic bag of this invention may be of the T-shirt type
having a generally U-shaped cut out in the top area of the bag to produce
laterally
spaced handles extending upwardly from the top area of the bag, or it may be
of
the type having a cut out defining a hole of sufficient size in generally a
central
area of the open top area of the bag for receiving fingers of the user and to
function
as a handle. This hole may preferably be kidney-shaped. Other types of plastic
bags having handles including cut out portions of the front and rear wall
sections
may be utilized in the invention of the present application.
The reduced strength regions caused by the cut out of the handle means of
the bag typically extends completely around a cut out hole in that type of bag
and
generally at the corners of a U-shaped cut out utilized in a T-shirt style
bag. The
closely spaced micro-perforations may extend in horizontal rows across the
entire
width of the bag and only below the reduced strength regions created by the
cut out
of the wall sections, or the closely spaced micro-perforations may extend in
vertical rows along the entire length of the bag and only on each side of the
reduced strength section regions created by the cut out of the wall sections.
The
micro-perforations preferably are about 1/32" in diameter and are preferably
spaced apart approximately 1/4". Other patterns, spacings and sizes may be
used
which accomplish the desired objectives of the present invention.
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By overcoming ventilation and strength problems in plastic bags proposed by
use in the fast food industry, it has also been found by this invention that
other
preferred features of plastic bags heretofore utilized in other contexts can
also be
utilized with the ventilated plastic bag of this invention. These improvements
include
the use of non-residue central mounting tab portions on the bags for adapting
the bags
for mounting on a suitable dispenser rack for removal by a user without
leaving
residue on the rack, self opening features which allow the bags to be serially
opened
one at a time by the user when removing the bags from a rack, angle seals at
the
bottom corners of the bag to produce a flat bag when the bag is in an open
position for
loading by a user, etc. It has also been found desirable to utilize either
clear film to
enable identification of articles placed inside the bag for a more accurate
order filling
in the fast food restaurant or co-extruded film in which an inside layer of
film is of a
stiffer material to provide shape to the bag and an outside layer is of a
softer film
material to enhance corona and pressure bonding between outside layers for
self
opening of the bags when serially removed one at a time from a bag pack
mounted on
a dispensing rack.
According to one aspect of the invention, there is provided a ventilated
plastic
bag particularly adapted for carrying hot food from fast food restaurants and
comprising:
front and rear wall sections connected together to define a closed bottom area
and an open top area;
handle means provided in the top area and at least partially formed by a cut
out of the front and rear wall sections creating reduced strength regions with
resulting
high potential for tearing in the front and rear wall sections around at least
part of the
cut out; and
closely spaced micro-perforations extending through the wall sections in at
least a major portion of the plastic bag other than the reduced strength
regions to
provide ventilation to an interior food carrying area of the plastic bag while
not
further weakening the reduced strength regions and increasing the potential
for
tearing.
According to another aspect of the invention, there is provided a ventilated
plastic bag particularly adapted for carrying hot food from fast food
restaurants and
comprising:
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CA 02344724 2001-09-19
front and rear wall sections connected together to define a closed bottom area
and an open top area;
handle means provided in the top area and at least partially formed by a cut
out of the front and rear wall sections defining a hole of sufficient size to
receme
~ fingers of a user and creating reduced strength regions with resulting high
potential
for tearing in the front and rear wall sections around at least part of the
cut out; and
closely spaced micro-perforations extending through the wall sections in at
least a major portion of the plastic bag other than the reduced strength
regions to
provide ventilation to an interior food carrying area of the plastic bag while
not
further weakening the reduced strength regions and increasing the potential
for
tearing.
According to a further aspect of the invention, there is provided a ventilated
plastic bag of the T-shirt type and particularly adapted for carrying hot food
from fast
food restaurants and comprising:
front and rear wall sections, gussetted side wall sections integrally
connecting
the front and rear wall sections together to define an open top area in the
bag, means
connecting bottoms of the front, rear and gussetted side wall sections
together to
define a closed bottom area;
laterally spaced handles integral with the front, rear and gussetted side wall
sections and extending upwardly from the open top area of the bag and being at
least
partially formed by a generally U-shaped cut out of the front, rear and
gussetted wall
sections creating reduced strength regions with resulting high potential for
tearing in
the front and rear wall sections around at least part of the cut out; and
closely spaced micro-perforations extending through the wall sections in at
least a major portion of the plastic bag other than the reduced strength
regions to
provide ventilation to an interior food carrying area of the plastic bag while
not
further weakening the reduced strength regions and increasing the potential
for
tearing.
Other features may also be combined with the novel ventilated plastic bag of
this invention to provide synergistic results.
Brief Description of the Drawings
Some of the objections and advantages of the invention having been set forth,
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CA 02344724 2001-09-19
other objects and advantages will appear from the following Detailed
Description Of
Preferred Embodiments Of The Invention, when taken in conjunction with the
accompanying drawings, in which:
FIG. I is a perspective view of a first embodiment of a ventilated plastic bag
constmcted in accordance with this invention, loaded with hot food from a fast
food
restaurant and being carried at a handle section by a user;
FIG. 2 is a perspective view of a pack of the plastic bags of the first
embodiment of FIG. 1 and having a first pattern of closely spaced micro-
perforations
and being mounted on a rack for removal by a user and filling with hot food
from a
fast food restaurant;
FIG. 3 is an enlarged front elevational view, partially broken away, of one of
tl - . . ,.., ,- . ,_ ~~______~ :"_...~..,....a :~ err= ~.
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CA 02344724 2001-04-20
FIG. 4 is a sectional view through the plastic bag of the first embodiment of
FIG. 3 and taken generally along the line 4-4 of FIG. 3;
FIG. S is an enlarged front elevational view of the top area of the first
embodiment of ventilated plastic bag of FIG. 3 and schematically illustrating
reduced strength regions created by the cut out of the front and rear wall
sections to
create a handle means in the plastic bag;
FIG. 6 is a view, like FIG. 3, illustrating a different pattern of closely
spaced micro-perforations;
FIG. 7 is a sectional view, taken generally along the lines 7-7 of FIG. 6;
FIG. 8 is a perspective view of the bag pack o~ FIG. 2 mounted on a
dispensing rack and showing the bags being serially removed one at a time from
the rack;
FIG. 9 is a front elevational view of a second embodiment of a ventilated
plastic bag of the T-shirt type construction and having the first pattern of
closely
spaced micro-perforations;
FIG. 10 is a perspective view of a pack of the bags of FIG. 9 mounted on a
dispensing rack; and
FIG. 11 is a view like FIG. 10 illustrating a first bag being opened on said
rack for filling by a user and subsequent removal for serially opening the
next bags
in the pack on the rack.
Detailed Description Of Preferred Embodiments Of The Invention
Refernng now to the drawings, there are shown two embodiments of
ventilated plastic bags, generally indicated at 10, in FIGS. 1-8 and FIGS. 9-
11,
respectively, which are particularly adapted for use in carrying hot food from
fast
food restaurants.
Each of these embodiments of plastic bags 10 include at least front and rear
wall sections 13, 14 connected together to define a closed bottom area 16 and
an
open top area 17, and handle means 20 provided in the top area 17 and which is
at
least particularly formed by a cut-out 21 of the front and rear wall sections
13, 14
creating reduced strength regions 25 with resulting high potential for tearing
in the
front and rear wall sections 13, 14 around at least a part of the cut-out 21.
Closely
spaced micro-perforations 30 extend through the wall sections 13, 14 in at
least a
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major portion of the plastic bag 10 other than the reduced strength regions 25
to
provide ventilation to an interior food carrying area of the plastic bag 10
(as
illustrated in FIG. 1 ), while not further weakening the reduced strength
regions 25
and increasing the potential for tearing of the bag 10.
Preferably, both of the embodiments of ventilated plastic bags 10 illustrated
in FIGS. 1-8 and FIGS. 9-11, respectively, further include gussetted side wall
sections 15 integrally connecting the front and rear wall sections 13, 14
together
and being positioned between these sections at side areas of the bag 10 in its
closed
position (as illustrated in FIGS. 2-10).
These plastic bags 10 may be constructed of any suitable material including
high-density polyethylene film material well known in the industry for use in
plastic bags. Preferably, the plastic bags 10 may be constructed of a clear
film
material, such as the polyolefin films normally used in plastic bag
manufacture, i.e.
low density, linear low density, medium density, high density polyethylene or
film
grade polypropylene. These films are produced from non-pigmented or natural
resin which is inherently non-opaque. The degree of film clarity will depend
upon
the type and density of resin used, however, all polyolefin films are
sufficiently
clear to allow the construction of bags which are relatively transparent. The
advantage of a clear film bag for fast food packaging are manifested in more
accurate order filling and by allowing the customer to readily inspect their
order
when packaged in the bags. The increased order accuracy and visual inspection
by
the customer allows for faster overall service and efficiency at the drive-
through
window of fast food restaurants.
A preferred embodiment of a clear film ventilated plastic bag 10 would be
the use of a primary high-density polyethylene resin film because of its
superior
stiffness, cost and processability. Polypropylene has a slightly higher
tensile
modulus, 165-200 kpsi, than high-density polyethylene, but is more difficult
to
process into bags and has a higher cost. Typical film grade high molecular
weight,
high-density polyethylene has a density in the range of .945-.955 gm/cu cm and
a
tensile modulus value of 150-160 kpsi. Typical film grade low density
polyethylene and linear low density polyethylene have a density range of .915-
.925
gm/cu cm and a modulus of 25-75 kpsi. The preferred film would be
manufactured from a commercial grade of high density polyethylene, such as
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CA 02344724 2004-11-12
Exxon HDZ-152 which has a density of .950 gmlcu cm, a modulus of 150 kpsi in
an average thickness of between I S-25 microns. Value for density and tensile
modulus are from the 1998-1999 volume of Plastic Technology - Manufacturing
Handbook And Buyers Guide.
The closed bottom area 16 of the bag 10 may be formed by heat sealing of
the film material utilized to form the bag 10 or in any conventional manner.
This
closed bottom area 16 may also include corner or angle seals 19 formed by heat
sealing and extending across corners of the bag 10 and through the front and
rear
wall sections 13, 14 and the intermediate gussetted side wall sections 15 to
define a
square bottom on the bag 10 when the bag is in an open position in a manner
well
understood by those with skill in the art.
Referring now specifically to the first embodiment of a ventilated plastic
bag 10 as shown in FIGS. 1-8, this bag 10 utilizes a handle means 20 which
includes a cut out 21 defining a hole of sufficient size to receive fingers of
a user
I S (as shown particularly in FIG. 1 ). This hole formed by the cut out 21 is
preferably
generally kidney-shaped and is positioned generally centrally of the top area
17
and between the gussetted side walls 15 of the bag 10. This cut out 21 creates
reduced strength regions 25 around the hole created by the cut out 21 (as
schematically shown in FIG. 5) which results in a higher potential for
tearing.
Referring now to the second embodiment of ventilated plastic bag 10
illustrated in FIGS. 9-11, this bag includes laterally spaced handles 20
integral with
the front, rear and gussetted side wall sections 13, 14, 15 and extending
upwardly
from the open top area l7 of the bag 10. These handles 20 are formed by a
generally U-shaped cut out 21 of the front, rear and gussetted side wall
sections 13,
14, 15 (as shown in FIG. 9) which creates reduced strength regions 25 with
resulting high potential for tearing around at least part of the cut out 21
(as
schematically indicated in FIG. 9)
The reduced strength regions 25 of the first embodiment of ventilated
plastic bag 10 of FIGS. 1-8 (which is created by the cut out 21 forming a hole
in
the top area of the bag 10 and which is preferably kidney-shaped) extends
completely around the cut out 21 hole forming part of the handle 20 (as
indicated
in F1G. 5). In the second embodiment of a T-shirt type ventilated plastic bag
of
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CA 02344724 2004-11-12
FIGS. 9-11, the reduced strength regions 25 are located generally at the
corners of
the U-shaped cut out 21 (as indicated in FIG. 9).
The closely spaced micro-perforations 30 may extend in horizontal rows
across the entire width of the bag 10 and only below the reduced strength
regions
25 created by the cut out 21 of the wall sections 13, 14, 15 (as shown in
FIGS. 1-5
and 8-1 1). Alternatively, the closely spaced micro-perforations 30 may extend
in
vertical rows along the entire length of the bag 10 and only on each side of
the
reduced strength regions 25 created by the cut out 21 of the wall sections
13,14,
15 (as shown in FIGS. 6 and 7). This latter pattern of closely spaced micro-
perforations 30 may also be utilized in the second embodiment of a T-shirt
style
plastic bag 10 of FIGS. 9-1 1. Preferably, the closely spaced micro-
perforations 30
in either pattern are spaced apart approximately 1/4" and are approximately
1/32"
in diameter.
Either embodiment of ventilated plastic bags 10 are preferably connected
together to form a pack of a plurality of such bags 10 (as shown in FIGS. 2,
8, 10
and 11 ). These packs of bags 10 may be mounted on suitable racks 50 (as shown
in FIGS. 2, 8, 10 and 11 ). For this purpose, each of the bags 10 includes a
detaching central mounting tab portion 18 having an aperture 26 therein for
mounting on an elongate generally horizontally extending central tab retaining
device 51 on the rack 50. This detaching central mounting tab portion 18 may
be
constructed in accordance with the teachings of assignee's U.S. Patents
5,845,779
and 5,881,882 provide a detaching central mounting tab portion 18 which is
adapted
to leave no residue on the rack 50 as the bags 10 are successively removed one
at a
time from the rack 50 for use by a user. The T-shirt type plastic bag 10 of
FIGS 9-11
also includes apertures 28 in the handles 20 for slideably mounting the bag
handles 20
on arms 52 on the rack 50 for purposes well known to those with skill in the
art.
Additionally, there is provided a means, such as a knick 27, in the tab
portion 18
for propagating a tear through the tab portion 18 from the aperture 26 to
ensure that
no bag residue is left on the dispensing rack 50 or the tab retaining device
51 as
disclosed in the above mentioned U.S. Patents 5,845,779 and 5,881,882.
It has also been found that it is preferable to incorporate into the pack of
plastic bags 10 of this invention the easy-open, self opening features set
forth in
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CA 02344724 2004-11-12
assignee's prior U.S. Patent 5,335,788. For this purpose, each of the bags 10
in the
pack are connected together by suitable compression areas 24 which extend
transversely through the bag pack in the upper portions of the bags such that
the bag
pack has decreased thickness in the compression area. The outer surfaces of
the front
and rear wall sections 13, 14 are corona treated (as fully disclosed in this
prior patent)
so that the corona treated outer surfaces of the front and rear wall sections
13,14 in
the localized compressed areas 24 are substantially releasably adhered
together and
adjacent inside surfaces of the front and rear wall sections 13,14 in the
compressed
1 o areas 24 which are not corona treated are not substantially adhered
together. This
construction provides self opening bags in the pack as the bags 10 are
serially
removed from the rack 50, as shown in FIG. 8 and 11 and as disclosed in the
above
mentioned U.S. Patent 5,335,788.
In this regard, it has been determined that corona induced pressure bonding
for self opening is easier to create with lower density film materials. It is
believed
that this is because of the inherent softness and molecular structure of these
lower
density film materials. However, in construction of plastic bags for packaging
hot
foods, stiffness of the bag is also a significant concern. Stiffness is
important to
make the bag stand-up and have shape to package the food in an orderly
fashion.
Stiffness also aids in venting of the bag by maintaining the top in an open
configuration. If the bag walls collapse, venting air flow will be restricted
and will
increase the likelihood of condensation of moisture within the bag. Film
stiffness
is determined primarily by the thickness of the film and the modulus
properties of
the particular resin being used to construct the film. Of these two factors,
thickness has the greatest influence but unfortunately also carries the
highest cost,
i.e. thicker bags equal more material equal higher price. Therefore, the
requirement for a stiff bag and a bag that will self open have somewhat
conflicting
requirements.
A suitable film structure which would meet these requirements has found to
be a co-extruded film structure including an inner layer of stiff material
such as
high molecular weight, high density polyethylene or polypropylene and a softer
outer layer such as low density polyethylene or linear low density
polyethylene.
Typical co-extruded structures consist of 70-75% of the total thickness coming
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CA 02344724 2001-04-20
from the inner layer and 25-30% of the total thickness coming from the outer
layer.
The preferred embodiment for this application to maximize stiffness and corona
pressure bonding would be an inner layer of high molecular weight, high
density
polyethylene, such as commercial grade Exxon HDZ-152, at 75% of the total
thickness, and an outer layer of linear low density polyethylene, such as
Exxon LL-
1108, at 25% of the total thickness. While this has been determined to be the
preferred embodiment of co-extruded film for optimizing both stiffness and
self
opening, other combinations of co-extruded film structures are certainly
possible to
meet the objectives of this invention.
In the drawings and specification there have been set forth preferred
embodiments of this invention, and although specific terms are employed, they
are
used in generic and descriptive sense only and not for purposes of limitation,
the
scope of the invention is defined in the following claims.
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